High-insulation transformer oil fire safety extinguishing agent and application system thereof

Abstract

The invention provides a high-insulation transformer oil fire safety extinguishing agent and an application system thereof. On the basis of a two-phase cooling-chemical blocking synergistic mechanism, an environment-friendly additive RF203 and ammonium polyphosphate (APP) are compounded, rapid refrigeration is achieved through solid-liquid-gas multi-phase-change latent heat absorption of the RF203, and a combustion chain in flame is cut off by means of NH2 and PO free radicals generated by decomposition of the APP, so that the purpose of efficient fire extinguishing is achieved.

Description

Technical Field

[0001] The invention relates to the field of fire extinguishing agents, in particular to a high-insulation transformer oil fire safety fire extinguishing agent and an application system thereof. Background Art

[0002] Transformers are the hub equipment of power systems and play a vital role in the transmission and distribution of electric energy. Transformers are usually filled with a large amount of mineral insulating oil, which serves as both an insulating medium and heat dissipation and cooling. However, mineral oil is a flammable material. Once it leaks and catches fire, it can easily cause a serious fire accident. According to statistics, fire is the main form of disaster for transformers, accounting for more than 40% of total accidents. Among the many transformer fires, oil fires are the most dangerous. Once formed, they are often accompanied by a large amount of thick smoke and violent combustion, with high thermal radiation intensity, fast spread speed, and extremely difficult to extinguish.

[0003] In view of the serious hazards of transformer oil fire, domestic and foreign scholars have conducted a lot of research. Traditional fire extinguishing methods mainly include foam fire extinguishing, dry powder fire extinguishing, gas protection, etc. However, foam is easily destroyed by high-temperature oil fire, dry powder is easy to cause secondary pollution, and gas fire extinguishing is slow to take effect. These methods are difficult to quickly and effectively control the spread of oil fire. In recent years, some new fire extinguishing agents such as halogenated hydrocarbons and aerosols have been introduced, showing advantages in extinguishing conventional liquid fires, but for special combustibles such as transformer oil with low ignition point and fast volatilization, it is still difficult to achieve ideal fire extinguishing effect.

[0004] The fundamental reason why conventional fire extinguishing agents are difficult to quickly extinguish transformer oil fires is that they have insufficient cooling capacity and lack an effective flame retardant mechanism. Most fire extinguishing agents rely mainly on single physical cooling or oxygen isolation asphyxiation to suppress flames. For oil fires, which have strong radiant heat feedback and fast flame propagation, it is difficult to fundamentally curb the spread of fire. At the same time, due to the lack of chemical flame retardant effects, the remaining combustibles are very easy to reignite, and in severe cases, they may even cause multi-point chain explosions. Therefore, in order to fundamentally solve the problem of transformer oil fire fighting, it is necessary to develop a new type of fire extinguishing agent that combines efficient cooling and chemical flame retardancy, and through dual synergy, achieve rapid and efficient extinguishing of oil fires. This is an important prerequisite for ensuring the inherent safety of the power system, and it has great and far-reaching significance for improving the national energy security level and promoting the sustainable development of the economy and society.

[0005] There have been a few studies on efficient and environmentally friendly fire extinguishing agents abroad, and some progress has been made. The U.S. Naval Research Laboratory has developed an oil-in-water emulsion fire extinguishing agent that uses emulsification to inhibit the volatilization of oil products, and has initially shown a certain fire extinguishing effect. The University of Glasgow in the UK proposed the use of nano-scale alumina particles to modify foams, using the high specific surface area of ​​nanomaterials to enhance heat absorption and improve the high temperature resistance of foams. Moscow State University in Russia prepared aerogel microspheres doped with diammonium dihydrogen phosphate, using a porous structure to achieve the dual effects of physical adsorption and chemical flame retardancy, showing good application prospects in extinguishing diesel fires. Overall, the above studies have certain innovations, but have not yet formed a systematic and mature fire extinguishing solution, and there is still a big gap from practical application.

[0006] Domestic research on new fire-extinguishing materials started late, but has developed rapidly. Tianjin University used the quenching phase separation method to prepare an aqueous solution of fluorinated surfactants, which has excellent surface tension characteristics and can effectively inhibit the combustion of polar flammable liquids. China University of Mining and Technology proposed a formula for a water-based fire extinguishing agent modified by carbon nanotubes. Through the interfacial effect of nanomaterials, the comprehensive performance of the fire extinguishing agent was significantly improved. Wuhan University of Technology conducted a study on the fire extinguishing mechanism based on multiphase fluid dynamics, revealing the multi-scale evolution of the aerosol fire extinguishing process, and providing important theoretical guidance for the design of new fire extinguishing agents. Although these studies have made gratifying progress, they are mainly aimed at general flammable liquids and rarely involve special media such as transformer oil. In addition, most of the above achievements remain in the laboratory stage, and engineering application cases are relatively rare.

[0007] In summary, traditional fire extinguishing agents can no longer meet the increasingly severe needs of transformer oil fire prevention and control, and it is urgent to develop new, efficient and environmentally friendly special fire extinguishing technologies. It is in this context that the present invention proposes a new transformer oil fire extinguishing agent based on a two-phase cooling-chemical blocking synergistic mechanism. In terms of medium selection, the environmentally friendly additive RF203 is used as a two-phase coolant, and the strong latent heat absorption brought by its solid-liquid phase change at room temperature and liquid-gas phase change at high temperature is utilized to achieve rapid cooling and fire extinguishing. In terms of flame retardant design, the high-efficiency flame retardant ammonium polyphosphate (APP) is introduced, and the NH2 and PO free radicals released during its high-temperature decomposition process are utilized to cut off the combustion chain in the flame, thereby inhibiting the spread of the fire. The two mechanisms of two-phase cooling and chemical flame retardancy are organically combined to form a synergistic effect, which can significantly improve the speed and reliability of fire extinguishing. The present invention systematically carries out research on the fire extinguishing agent from four aspects: material preparation, performance testing, mechanism analysis and application evaluation, in order to provide a set of effective solutions for transformer oil fire prevention and control. Summary of the invention

[0008] Based on the above problems, the present invention provides a high-insulation transformer oil fire safety extinguishing agent.

[0009] The fire extinguishing agent of the present invention is compounded by the following components in a specific ratio:

[0010] Dual phase change material RF203 (octadecanoic acid), as the main cooling component, mass fraction 15%

[0011] Chemical flame retardant ammonium polyphosphate (APP), promotes combustion chain breaking, mass fraction 10%

[0012] Thickener hydroxyethyl cellulose (HEC), improves suspension and coverage, mass fraction 0.5%

[0013] Surfactant sodium dodecyl sulfate (SDS), reduces surface tension and promotes spreading, mass fraction 0.5%

[0014] Antifreeze agent ethylene glycol, to ensure stable performance in low temperature environment, mass fraction 5%

[0015] Antifoaming agent polydimethylsiloxane (PDMS), to prevent excessive foaming during use, mass fraction 0.5%

[0016] Deionized water, as the basic liquid medium of fire extinguishing agent, with the remainder being the mass fraction.

[0017] The preparation process is as follows:

[0018] Step 1: Raw material pretreatment:

[0019] The dual phase change material RF203 and the flame retardant ammonium polyphosphate (APP) were ground to less than 300 mesh (about 48 microns) to ensure their dispersibility in water. At the same time, other liquid additives such as SDS, PDMS, ethylene glycol, etc. were filtered to ensure purity.

[0020] Step 2: Prepare the base dispersion:

[0021] First, add a certain amount of deionized water into a clean stainless steel mixing kettle and heat it to about 40°C. Then add thickener hydroxyethyl cellulose (HEC), antifoaming agent PDMS, and surfactant SDS in sequence, and stir slowly to fully dissolve them. Continue to add antifreeze agent ethylene glycol, adjust the stirring speed to 200r / min, and stir at a constant temperature for 20 minutes to mix all components evenly. A clear, transparent, flocculation-free and precipitated basic dispersion is obtained.

[0022] Step 3: High-speed dispersion of solid powder:

[0023] Slowly add the pre-treated RF203 and APP powders to the base dispersion, increase the speed to 1500r / min, and vigorously stir and disperse for 30 minutes. Under the action of high-speed shear, the RF203 and APP particles are fully wetted and evenly dispersed in the solution to form a stable suspension. At the same time, high-speed stirring can further promote the compatibility between the components.

[0024] Step 4: Homogenization and emulsification:

[0025] The mixed solution was transferred to a homogenizer and emulsified for 3 times at a pressure of 50 MPa. The purpose of high-pressure homogenization is to further break the RF203 and APP particles to submicron level through strong shearing and collision, and to coat the surface with a layer of surfactant molecules to form stable emulsified particles. This is a key step to achieve long-term stability and resistance to precipitation and aggregation.

[0026] Step 5: Add antiseptic and mildew preventer:

[0027] In order to improve the storage stability of the product, an appropriate amount of preservative and mildew preventer needs to be added. The present invention selects compounded benzalkonium bromide and isothiazolinone preservatives, with mass fractions of 0.2% and 0.1% respectively. It is directly added to the emulsified mixed solution and stirred for 5 minutes to completely dissolve.

[0028] Step 6: Conditioning and Filtration:

[0029] After the mixed liquid is left to stand at room temperature for 2 hours, its viscosity, pH value, conductivity and other indicators are tested and compared with the process indicators. If there is a deviation, it can be tempered by adding an appropriate amount of thickener, acid-base regulator, etc. After that, the product is filtered by a vibrating screen to remove possible undispersed agglomerates and impurities. The filter mesh size is 325 mesh (about 45 microns).

[0030] Step 7: Filling and sealing:

[0031] The finished fire extinguishing agent liquid after conditioning is filled into clean stainless steel barrels or plastic barrels, with a net weight of 50kg per barrel. The packaging barrels must be made of high-quality food-grade materials and strictly cleaned and dried. After filling, tighten the barrel cover and apply a lead seal or plastic seal on the barrel mouth to ensure sealing and anti-theft.

[0032] Step 8: Label identification:

[0033] The product certificate label is pasted on the surface of the packaging barrel. The label content includes: product name, main ingredients, implementation standards, production date and batch number, shelf life, storage conditions, usage, precautions, manufacturer, service hotline, etc. At the same time, the dangerous goods logo and UN number are sprayed or pasted on the front of the barrel to meet the transportation and management requirements of fire protection products.

[0034] Step 9: Finished product inspection:

[0035] The finished product after filling shall be inspected according to the sampling plan, and the test items include: suspension, viscosity, pH value, density, conductivity, foam multiple, 25% fire extinguishing time, surface tension, low temperature stability, metal corrosion, etc. The inspection results must meet the product technical requirements and fill in the quality inspection report.

[0036] Step 10: Packing and storage:

[0037] The qualified products are packed in boxes, each box contains 2 barrels, a total of 100kg. The outer packaging is a thickened corrugated box lined with a plastic film bag. The product name, quantity, implementation standard and other labels are sprayed or pasted on the outside of the box. After packaging, it is transported to the finished product warehouse and neatly stacked by batch. The warehouse must meet the requirements of ventilation, drying, moisture and sun protection, and regular temperature, humidity and hygiene inspections.

[0038] The transformer oil fire extinguishing agent of the present invention has the following significant technical advantages: first, it breaks through the limitation of the traditional single fire extinguishing mechanism, creatively couples the two mechanisms of dual phase change cooling and chemical flame retardancy to complement each other, can quickly cool down, and can cut off the flame combustion chain, and jointly curb the spread of fire from the two dimensions of heat and power. Secondly, the formula is scientific and reasonable, green and environmentally friendly, the components are widely available, the production process is simple, and it can be mass-produced, with good application economy. Furthermore, it overcomes the defects of conventional fire extinguishing agents such as poor cooling effect, weak suffocation effect, and easy re-ignition. The fire extinguishing speed is more than 3 times that of similar products, and the ability to completely extinguish fires is stronger. Finally, it is friendly and harmless to equipment and the environment. After the fire is extinguished, the electrical properties of the oil and the insulation properties of the equipment are not affected, which can ensure the safe and stable operation of the power grid, and the comprehensive benefits are significant. DETAILED DESCRIPTION

[0039] The composition of this fire extinguishing agent mainly includes three categories: two-phase coolant, chemical flame retardant and basic additives. Among them, the selection of two-phase coolant is crucial and directly determines the refrigeration performance of the fire extinguishing agent. After a large amount of literature research and repeated experiments in the early stage, RF203 was finally determined to be used as the two-phase coolant. The chemical name of RF203 is octadecanoic acid, and its molecular formula is , is a higher fatty acid. It is a white waxy solid at room temperature, with a melting point of 45°C, a boiling point of 269°C, and a latent heat of up to 183J / g. RF203 is non-toxic and harmless, widely available, and inexpensive. It is a phase change energy storage material with great application prospects. The present invention cleverly utilizes the solid-liquid-gas three-phase transition characteristics of RF203, so that it can play a cooling effect in different temperature ranges, thereby controlling the spread of fire in all directions. Specifically, RF203 particles are dispersed in the extinguishing agent base liquid in solid form at room temperature; when sprayed into the fire area, the solid RF203 quickly absorbs a large amount of heat and turns into liquid, effectively reducing the combustion temperature; as the temperature of the fire area continues to rise, the liquid RF203 further absorbs heat and vaporizes, and the volume suddenly expands by more than 1,600 times, not only taking away a large amount of heat, but also isolating combustibles from air and blocking the combustion chain. In this way, RF203 forms two significant endothermic peaks near its melting point and boiling point, thereby achieving full-process refrigeration and fire extinguishing. Compared with single phase change materials, the solid-liquid-gas multi-stage heat absorption of RF203 greatly improves the cooling efficiency, which is a major innovation of this fire extinguishing agent.

[0040] The selection of chemical flame retardants is also crucial. Among many flame retardants, ammonium polyphosphate (APP) stands out for its high efficiency, environmental protection, and wide sources. The chemical formula of APP is APP is an inorganic polymer. APP undergoes a deamination reaction at 300-400°C, releasing a large amount of NH3, and then decomposes into NH2 free radicals; at 400-500°C, a polycondensation reaction occurs to generate polymetaphosphoric acid and PO free radicals. These active groups can quickly kill free radicals such as H and OH in the flame, thereby cutting off the combustion chain and inhibiting the spread of the fire. At the same time, the thermal decomposition of APP will also form a glass-like heat-insulating and oxygen-blocking film on the combustion surface, further isolating the contact between the combustible gas and the flame. In addition, APP can also absorb a large amount of heat during the high-temperature decomposition process, playing a physical cooling role. It can be seen that APP can curb the fire in all directions with its unique chemical and physical flame retardant effects. Introducing such an excellent chemical flame retardant into the transformer oil fire extinguishing agent will undoubtedly greatly improve the performance of the fire extinguishing agent. This is also another highlight of the present invention.

[0041] After determining the key functional components, the present invention also selects a variety of basic additives, including thickeners, surfactants, antifreeze agents, foam suppressants, etc., to improve the physicochemical properties and performance of the fire extinguishing agent. The thickener uses hydroxyethyl cellulose (HEC) to improve the suspension and coverage of the fire extinguishing agent; the surfactant uses sodium dodecyl sulfate (SDS) to reduce the surface tension and promote the spreading of the fire extinguishing agent on the oil surface; the antifreeze agent uses ethylene glycol to ensure the stable performance of the fire extinguishing agent in a low temperature environment; the foam suppressant uses polydimethylsiloxane (PDMS) to prevent excessive foam from being generated during use and affecting the spraying. Although the addition of the above components does not directly participate in the fire extinguishing process, it is very important to improve the comprehensive performance of the fire extinguishing agent. Based on the principle of "less is better than more, just enough is good", a large number of orthogonal experiments are used to optimize the dosage of each component, and the basic formula of the fire extinguishing agent is finally determined as follows: RF20315%, APP 10%, HEC 0.5%, SDS 0.5%, ethylene glycol 5%, PDMS 0.5%, and the balance is water.

[0042] The preparation process of the fire extinguishing agent is as follows: first, grind RF203 and APP to less than 300 meshes respectively to ensure their dispersibility; then add deionized water, ethylene glycol, and HEC in turn and stir evenly; then slowly add RF203 and APP powders, disperse at high speed for 30 minutes, so that the particles are evenly dispersed; finally, add SDS, PDMS and other additives, continue to stir for 15 minutes, and a uniform and stable fire extinguishing agent product is obtained. The process is simple and easy to implement, all raw materials and equipment are conventional products, and large-scale production can be achieved, which has a good application prospect.

[0043] The main physical and chemical properties of the prepared fire extinguishing agent samples were tested, and the results are shown in Table 2. It can be seen that the fire extinguishing agent is similar to water in density, viscosity, pH value, etc., which is conducive to pumping and spraying. The electrical conductivity is slightly higher than water, but much lower than salt water, and will not corrode equipment pipelines. The refractive index is close to that of water, and the optical properties are excellent, which does not affect the observation of the fire. These properties are better than conventional dry powder and foam fire extinguishing agents.

[0044] ;

[0045] Table 2 Main physical and chemical properties of fire extinguishing agents

[0046] In addition, we also examined the microscopic morphology and particle size distribution of RF203 and APP particles. As shown in Table 3, RF203 particles are approximately spherical, with a rough and porous surface, which is conducive to their full heat absorption; the particle size is mainly concentrated in 5-15um, and the average particle size is 8.7um. APP particles are slightly irregular, with an obvious layered structure on the surface, which is the microscopic basis for their flame retardant effect; the particle size distribution is 10-30um, and the average particle size is 22.3um. The particle size distribution of the two particles is reasonable, which not only ensures good dispersibility, but also does not significantly increase fluid resistance. Overall, this fire extinguishing agent exhibits excellent characteristics in both microstructure and macroscopic properties, laying a solid foundation for its efficient fire extinguishing.

[0047] ;

[0048] Table 3 Micromorphology and particle size distribution characteristics of RF203 and APP particles

[0049] In order to systematically evaluate the performance of the fire extinguishing agent, we built an experimental device as shown in Table 4. The main body is a stainless steel fire extinguishing cabin with a volume of 1m3, which contains 250mL of transformer oil. An ignition device, a thermocouple, and a pressure sensor are set up for ignition, temperature measurement, and pressure measurement, respectively. The fire extinguishing agent is fed into the spray gun by an air pressure pump, the nozzle diameter is 2mm, and the spray pressure is 0.6MPa. 200mL of fire extinguishing agent is taken for each experiment. The spraying starts 2min after ignition, and the parameters such as the fire extinguishing time (from the start of spraying to the flame extinguishing), oil temperature change, and cabin pressure are recorded. Each group of experiments is repeated 5 times and the average value is taken.

[0050] ;

[0051] Table 4 Fire extinguishing test device parameters

[0052] The experimental process is as follows:

[0053] (1) Place 250 mL of transformer oil in the fire extinguishing chamber and heat it to 150°C to simulate the overheated oil surface;

[0054] (2) Ignition to form a stable oil surface fire;

[0055] (3) Continue heating for 2 minutes until the fire develops fully;

[0056] (4) Turn on the fire extinguishing system and record the changes of various parameters over time until the flame is extinguished;

[0057] (5) Observe for 5 minutes and record the re-ignition situation;

[0058] (6) Weigh the residual oil and calculate the oil loss rate.

[0059] For comparison, the same experiment was carried out using water, foam fire extinguishing agent (6% type) and dry powder fire extinguishing agent (monoammonium phosphate based).

[0060] Table 5 gives a comparison of the extinguishing time and re-ignition rate of different fire extinguishing agents. It can be seen that the average extinguishing time of this fire extinguishing agent is the shortest (15.6s), which is only 1 / 8 of clean water, 2 / 5 of foam, and 1 / 2 of dry powder, and the advantage is very significant. Moreover, this fire extinguishing agent can stably extinguish the fire, and there is no re-ignition within 5 minutes, while the other three fire extinguishing agents all have re-ignition to varying degrees, among which the re-ignition rate of clean water and foam even exceeds 50%. Such a large difference is mainly due to the lack of effective cooling and flame retardant effects of conventional fire extinguishing agents. Although clean water has a certain cooling effect, its heat capacity is limited and it is difficult to cool down quickly; foam is easily destroyed by high-temperature flames and is not tightly covered; although dry powder can isolate the air, the heat cannot be taken away in time. These factors all lead to the easy re-ignition of residual combustibles. In contrast, RF203 in this fire extinguishing agent can strongly absorb heat and quickly cool down and extinguish the fire; APP can cut off the flame combustion chain and inhibit re-ignition. The two work together to curb the spread of fire from both thermal and dynamic levels. It can be seen that the organic combination of efficient cooling and chemical flame retardancy is the key to the rapid and reliable effect of this fire extinguishing agent.

[0061] ;

[0062] Table 5 Comparison of fire extinguishing time and re-ignition rate of different fire extinguishing agents

[0063] Table 6 further compares the changes in oil temperature during the extinguishing process of different fire extinguishing agents. It can be seen that when this fire extinguishing agent is used, the ignition point temperature drops the fastest, and it only takes 12 seconds to drop from the flame temperature of about 900℃ to below 300℃, which is significantly faster than other fire extinguishing agents. This is due to the excellent endothermic cooling effect of RF203. After the RF203 particles are sprayed into the fire area, the solid-liquid phase change latent heat is as high as 183kJ / kg, which is much higher than the vaporization latent heat of water (2260kJ / kg), so the cooling rate is much higher than other fire extinguishing agents. In addition, RF203 further absorbs heat and vaporizes, taking away a lot of heat from the flame. Such strong double heat absorption is the direct reason for its rapid cooling and fire extinguishing. In contrast, the cooling effect of conventional fire extinguishing agents is much weaker. Clear water and foam mainly rely on the evaporation of water to absorb heat, while dry powder has no significant cooling effect, so the temperature of the fire area drops slowly. It can be seen that the dual phase change endothermic cooling of RF203 is its biggest feature that is superior to conventional fire extinguishing agents.

[0064] ;

[0065] Table 6 Oil temperature changes under different fire extinguishing agents

[0066] Based on the above experimental results, it can be seen that this fire extinguishing agent is significantly superior to conventional fire extinguishing agents in terms of cooling and fire control, oxygen isolation and suffocation, and re-ignition inhibition. This is mainly due to the dual synergistic effect of RF203 and APP components. RF203 uses the strong latent heat absorption and volume expansion brought about by solid-liquid-gas multiphase transformation to quickly cool down and isolate the air; APP releases free radicals through high-temperature decomposition, effectively blocking the flame combustion chain and inhibiting the spread of fire. Such efficient physical cooling and chemical flame retardant mechanisms are the microscopic roots of the excellent performance of the fire extinguishing agent.

[0067] Considering that the final destination of the fire extinguishing agent is the environment and equipment, it is very important to evaluate its ecological safety and the protective effect on the equipment. The present invention conducted environmental compatibility and corrosiveness tests on the fire extinguishing agent. Mice were placed in a closed space filled with fire extinguishing agent and observed for 14 consecutive days. The survival rate of the mice was 100%, and no poisoning reaction was observed, indicating that the fire extinguishing agent has no acute toxicity to mammals. The chemical oxygen demand (COD) of the fire extinguishing agent is 682 mg / L, which is far lower than the national primary emission standard (1500 mg / L), indicating that it has little environmental impact and is easy to degrade.

[0068] In order to investigate the protective effect of fire extinguishing agent on equipment, metal sheets such as copper, aluminum and steel were immersed in fire extinguishing agent, heated at a constant temperature of (55±2)℃ for 30 days, and weighed every 7 days to determine the mass change. The results showed that the average corrosion rates of the three metals were 0.21, 0.34 and 0.16 mg / (dm2·day), respectively, which were all lower than the industry standard of 0.5 mg / (dm2·day), belonging to the excellent level. After treatment, the residual fire extinguishing agent had almost no effect on the key parameters of transformer oil such as breakdown voltage and volume resistivity. It can be seen that this fire extinguishing agent is not only environmentally friendly, but also can protect equipment well and can be used with confidence.

[0069] In order to deeply analyze the mechanism of action of fire extinguishing agents, theoretical analysis and numerical simulation were carried out, focusing on the heat and mass transfer process of RF203 and the chain blocking reaction kinetics of APP.

[0070] The process of RF203 particles melting and vaporizing under heat can be regarded as a non-steady-state heat and mass transfer problem. Assuming that the thermal conductivity inside the particles is constant, the initial temperature is uniform, and the heat and mass transfer is carried out in a spherical coordinate system, the process can be described by the following set of equations:

[0071] ;

[0072] In the formula, is the particle density, is the specific heat capacity, is the thermal conductivity, is the solid phase density, is the solid-liquid interface motion velocity. The boundary conditions and initial conditions are:

[0073] ;

[0074] In the formula, is the flame temperature, is the convective heat transfer coefficient, By solving the above equations, we can get the temperature field and solid phase distribution of RF203 particles at different times, and then calculate its heat absorption rate. and mass loss rate :

[0075] ;

[0076] Numerical calculations show that for RF203 particles with a particle size of 10 μm, the peak heat absorption power can reach 233 kW / g. In addition, the time required for RF203 from the beginning of heating to complete vaporization is only 32 ms, while water vaporization under the same conditions requires 1.2 s, indicating that RF203 responds more quickly. This quantitatively explains the excellent cooling effect of RF203.

[0077] Free radicals such as NH2 and PO generated by high-temperature decomposition of APP can effectively block the combustion chain reaction. The important reactions are as follows:

[0078] ;

[0079] The above reaction kinetic model was solved using Chemkin software, and the evolution of the concentration of free radicals such as H, OH, NH2, and PO in the flame over time was obtained: after the fire extinguishing agent was sprayed, the concentration of H and OH free radicals in the flame dropped rapidly, while the concentration of NH2 and PO rose rapidly. This shows that NH2 and PO produced by the decomposition of APP have captured a large amount of H and OH, cutting off the combustion chain, which is the main chemical flame retardant mechanism. Further analysis found that the contribution rates of NH2 and PO to the inhibition of the combustion rate were 28% and 35%, respectively, and the two together dominated. It is worth noting that NH2 and PO can undergo a series of mutually reinforcing cyclic reactions with H and OH:

[0080] ;

[0081] This cyclic reaction allows NH2 and PO to be continuously regenerated, showing a quasi-catalytic effect, thereby continuously blocking the combustion chain. This is the unique advantage of APP compared to other flame retardants. In summary, the NH2 and PO free radicals produced by APP can quickly and efficiently inhibit combustion, complementing the physical cooling of RF203, which is the fundamental reason for the outstanding performance of the fire extinguishing agent.

[0082] In order to investigate the application effect of fire extinguishing agent in real power facilities, a field test was carried out in cooperation with a power supply company in a certain city. Five 110kV and above substations were selected as pilots, each equipped with 500kg of this fire extinguishing agent and an automatic sprinkler fire extinguishing system. During the continuous monitoring for one year, two transformer oil fires occurred.

[0083] The first one occurred at the bushing on the low-voltage side of the main transformer of a 220kV station. The fire was small in the early stage of the incident, and the fire extinguishing system was activated in time, extinguishing the open fire within 27 seconds. The whole process was stable and controllable. Only the bushing of the transformer was partially damaged, and it resumed operation after 3 days of maintenance. If it is not handled in time, it is very easy to cause a disaster.

[0084] Another incident occurred in a 10kV reactor at a 500kV station. The oil pillow was ignited due to breakdown discharge. After receiving the alarm, the local fire department used conventional fire extinguishing agents such as foam, but the effect was minimal. After the standby fire extinguishing agent was activated, the open fire was extinguished within 20 seconds. Although one reactor was burned, the whole unit was spared. After cleaning the insulating oil and replacing the damaged parts, the operation was resumed after 5 days.

[0085] The average extinguishing time of the two fires was 23.5s, which is consistent with the experimental results. After the fire was extinguished, the electrical performance test of the oil showed that its breakdown voltage, volume resistivity and other indicators still met the operating requirements. The equipment integrity rate reached more than 97%, and the direct economic loss was less than 500,000 yuan. Once the fire spread, the loss would be incalculable. It can be seen that this fire extinguishing agent can safely and effectively extinguish oil fires in power equipment, with significant economic and social benefits.

[0086] In response to the urgent need for transformer oil fire prevention and control, this paper develops a new type of fire extinguishing agent based on a two-phase cooling-chemical blocking synergistic mechanism. The main conclusions are as follows:

[0087] (1) By optimizing the dual phase change material RF203 and the flame retardant APP, a composite fire extinguishing agent with both high-efficiency refrigeration and chemical flame retardancy was prepared, which played a synergistic role of "1+1>2". The formula has excellent physical and chemical properties, is environmentally friendly, and can be mass-produced.

[0088] (2) Fire extinguishing experiments show that the average extinguishing time of this fire extinguishing agent is only 15.6 seconds, which is about 1 / 3 of conventional foam and dry powder fire extinguishing agents, and there is no re-ignition within 5 minutes; it can reduce the temperature of the fire area from 900°C to below 300°C in a short period of time, with a significant cooling effect; it can quickly dilute the combustible gas in the fire area and play a physical asphyxiation role. The comprehensive fire extinguishing performance comprehensively surpasses traditional fire extinguishing agents.

[0089] (3) Theoretical analysis reveals that RF203 achieves super-strong heat absorption and rapid oxygen isolation within microseconds by virtue of the high latent heat and large volume expansion of the solid-liquid-gas three-phase transition; APP decomposes at high temperature to produce NH2 and PO free radicals, which block the combustion chain by capturing H and OH, and exhibit a quasi-catalytic effect of cyclic regeneration. The two form a multiple synergy of thermal, dynamic and chemical forces.

[0090] (4) On-site applications have shown that the fire extinguishing agent can effectively extinguish oil fires in 110kV and above substations, with an average fire extinguishing time of 23.5s, an equipment integrity rate of over 97%, and direct economic losses reduced to a minimum, demonstrating great application value. With the establishment of a series of supporting fire extinguishing devices and intelligent prevention and control systems, it will surely become a powerful tool for oil fire prevention and control in transformers and related fields.

[0091] The innovative achievements of the present invention can be summarized into the following three points: First, it proposed and realized a new idea of ​​"cooling + flame retardant" composite fire extinguishing that is urgently needed in the field of transformer oil fire prevention and control, and opened up a research direction for unconventional fire extinguishing agents; second, it systematically explained the coupling mechanism of multi-phase change endothermic cooling and free radical chain blocking, enriched and developed the basic theory of multi-physical field collaborative fire extinguishing; third, it has been successfully applied in oil fire prevention and control in the power industry, creating a new intelligent fire extinguishing model involving multiple departments, and providing a strong guarantee for my country's power production safety.

Claims

1. A high insulation transformer oil fire safety extinguishing agent, characterized in that: The fire extinguishing agent is compounded by the following ingredients in specific proportions: Dual phase change material RF203 (octadecanoic acid), mass fraction 15% Chemical flame retardant ammonium polyphosphate (APP), mass fraction 10% Thickener: Hydroxyethylcellulose (HEC), mass fraction 0.5% Surfactant sodium dodecyl sulfate (SDS), mass fraction 0.5% Antifreeze agent ethylene glycol, mass fraction 5% Antifoaming agent polydimethylsiloxane (PDMS), mass fraction 0.5% Deionized water, as the base liquid medium of the fire extinguishing agent, the balance.

2. A high insulation transformer oil fire safety extinguishing agent as claimed in claim 1, characterized in that: The preparation method of the fire extinguishing agent is as follows: Step 1: Raw material pretreatment: Grind the dual phase change material RF203 and the flame retardant ammonium polyphosphate (APP) to below 300 mesh (about 48 microns) to ensure their dispersibility in water; at the same time, other liquid additives such as SDS, PDMS, and ethylene glycol are filtered to ensure purity. Step 2: Prepare the base dispersion: First, add a certain amount of deionized water into a clean stainless steel mixing kettle and heat it to about 40°C; then add thickener hydroxyethyl cellulose (HEC), antifoaming agent PDMS, and surfactant SDS in sequence, and stir slowly to fully dissolve them; continue to add antifreeze agent ethylene glycol, adjust the stirring speed to 200r / min, and stir at a constant temperature for 20 minutes to mix all components evenly; A clear and transparent basic dispersion without flocculation and precipitation is obtained; Step 3: High-speed dispersion of solid powder: Slowly add the pre-treated RF203 and APP powders into the basic dispersion, increase the speed to 1500r / min, and vigorously stir and disperse for 30 minutes; under the action of high-speed shear, the RF203 and APP particles are fully wetted and evenly dispersed in the solution to form a stable suspension; at the same time, high-speed stirring can further promote the compatibility between the components; Step 4: Homogenization and emulsification: The mixed liquid was transferred to a homogenizer and emulsified for 3 times at a pressure of 50 MPa. The purpose of high-pressure homogenization is to further break the RF203 and APP particles into submicron size through strong shearing and collision, and to coat the surface with a layer of surfactant molecules to form stable emulsified particles. This is a key step to achieve long-term stability and resistance to precipitation and aggregation. Step 5: Add antiseptic and mildew preventer: In order to improve the storage stability of the product, an appropriate amount of preservative and mildew preventer needs to be added; the present invention selects compounded benzalkonium bromide and isothiazolinone preservatives with mass fractions of 0.2% and 0.1%, respectively; directly add them to the emulsified mixed solution, and continue stirring for 5 minutes to completely dissolve them; Step 6: Conditioning and filtration: After the mixed liquid is left to stand at room temperature for 2 hours, its viscosity, pH value, and conductivity indexes are tested and compared with the process indexes; if there is a deviation, it can be conditioned by adding an appropriate amount of thickener and acid-base regulator; then the product is filtered by a vibrating screen to remove possible undispersed agglomerates and impurities, and the filter mesh aperture is selected to be 325 mesh (about 45 microns); Step 7: Filling and sealing: Fill the finished fire extinguishing agent liquid after conditioning into clean stainless steel barrels or plastic barrels, with a net weight of 50kg per barrel. The packaging barrels must be made of high-quality food-grade materials and must be strictly cleaned and dried. After filling, tighten the barrel cover and apply a lead seal or plastic seal to the barrel mouth to ensure sealing and anti-theft properties. Step 8: Label identification: Paste the product certificate label on the surface of the packaging barrel. The label content includes: product name, main ingredients, implementation standards, production date and batch number, shelf life, storage conditions, usage, precautions, manufacturer, and service hotline; at the same time, spray or paste the dangerous goods logo and UN number on the front of the barrel to meet the transportation and management requirements of fire protection products; Step 9: Finished product inspection: The finished products after filling shall be inspected according to the sampling plan. The inspection items include: suspension, viscosity, pH value, density, conductivity, foam multiple, 25% fire extinguishing time, surface tension, low temperature stability, and metal corrosion. The inspection results must meet the product technical requirements and fill in the quality inspection report; Step 10: Packing and storage: The qualified products are packed in boxes, each box contains 2 barrels, a total of 100kg; the outer packaging uses thickened corrugated paper boxes lined with plastic film bags; the product name, quantity, and implementation standard labels are sprayed or pasted on the outside of the box; after packaging, they are transported to the finished product warehouse and neatly stacked and stored by batches; the warehouse must meet the requirements of ventilation, drying, moisture-proof and sun-proof, and regular temperature, humidity and hygiene inspections are carried out.